Method of producing wood pulp including steaming, vacuum, and impregnation



Oct. 11, 1966 F. A. Lol-:BEL

METHOD OF PRODUCING WOOD PULP INCLUDING STEAMING, VACUUM, AND IMPREGNATION 2 Sheets-Sheet 1 Filed Feb. 14, 1963 STEAMING, VACUUM, AND IMPREGNATION 2 Sheets-Sheet 2 Filed Feb. 14, 1965 N.m:rL

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United States Patent 'Olice A3,278,367 Patented Oct. 11, 1966 3,278,367 METHOD OF PRODUCING WOOD PULP INCLUD- lNG STEAMING, VACUUM, AND llVIPREGNA- HON Frederick A. Loebel, Milwaukee, Wis., assigner to Aqua- Chem, Inc., a corporation of Wisconsin Filed Feb. 14, 1963, Ser. No. 258,466 2 Claims. (Cl. 162-19) This invention relates to a method for treating fibrous material with digesting liquors and more particularly t an improved method for impregnating wood chips with digesting liquors to remove the cementing bases therefrom.

As a primary step in producing paper products from wood chips, it is preferable that the wood be formed into chips and that the cementing substances, such as the lignins, pectins, and resins, may be removed therefrom to release the wood fibers as substantially pure cellulose. A common means of removing Vthe aforementioned cementing substances is to place the wood chips in a vertical digester and apply an appropriately known chemical solution. Several hours of digesting is required before the entire mass may be removed to another vat for rinsing away the dissolved cementing bases as well as the 4chemical solution. After rinsing, the raw pulp may th'en be formed into mats to be dried, or if it is made into paper, it is run through beaters which mix the bers and remove any lumps which may remain therein.

The principal chemical process used to remove the cementing bases are the sulphite, soda, sulphate and semichemical (or sodium sulphite and sodium bicarbonate) processes. The present cooking methods for these processes require long periods of soaking to suiciently impregnate wood chips with the aforementioned digesting liquors so that they might produce a high grade pulp.

It is therefore a primary object of this invention to provide a new and improved method for producing wood pulp.

It is another `object of this invention to provide a new and improved method for producing wood pulp comprising the continuous and successive steps of subjecting wood chips to vacuum and thence introducing a digesting liq-uor under pressure to impregnate the brous material thereby to remove the cementing bases therefrom.

It is another object of this invention to provide a new and improved method for producing wood pulp comprising the continuous and successive steps of preheating wood chips, then subjecting the chips to vacuum, then introducing a digesting liquor under pressure to impregnate th'e chips and remove the cementing bases therefrom.

It is still another object of this invention to provide a new and improved method for producing wood pulp comprising the steps of continuously passing a plurality of closed chambers past a feeding station at which wood chips are introduced therein and thence continuously and successively passing the chambers containing the wood chips past a preheating station at which said chips are preheated, then passing said wood chips past an evacuation station at which air is removed from th'e chambers, and thence passing said wood chips past an impregnation 4station at which hot digesting liquor is introduced to impregnate the chips thereby and thence passing the chips past a draining station at which the excess liquor is drained to the exterior, and thence discharging the chips from each chamber.

It is a further object of this invention to provide a new and improved method for producing wood pulp comprising the steps of preheating wood chips to a temperature not exceeding 200 F., thence subjecting the Wood chips to a vacuum of approximately 28" of mercury, and thence impregnating the chips with a digesting liquor at a pressure range of 50 to 20() p.s.i., thence draining the excess liquor from said chips to produce wood pulp thereby.

Other objects and advantages will be readily apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a partial perspective View of an apparatus for employing the method of this invention;

FIGURE 1A is a continuation of the device shown in FIGURE 1; and

FIGURE 2 is a block diagram of the method of this invention as employed by the apparatus shown in FIG- URES 1 and 1A.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail an embodiment of the invention with the understanding that the present disclosure is to beconsidered as an exemplication of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

As shown in the drawings an apparatus suitable for carrying out the method of this invention comprises a generally cylindrically shaped tube 10 mounted on a base 12 through which a plurality of pistons 14 mounted on a continuous belt 16 pass. The tube is a sutlicient length so that the entire process may be carried out within the length thereof. The belt has a plurality of pivotal `connections 18 throughout the length thereof and passes over suitable sprockets (not shown) at either end of the tube, one of which is driven by .a suitable motor 22 to drive the belt and piston in an endless path through the tube. A lower track 24 is provided below the tube to complete the circuitous path of the pistons and belt.

The tube is provided with an intake 26 into which fibrous materials, such as wood chips are fed, and a discharge 28 from which point the treated fibrous materials are expelled from the apparatus. The pistons 14 are in tight peripheral engagement with the internal diameter of the t-ube 10 and form therewith a continuous series of movable chambers 20.

The tube, in conjunction with the chambers 20 formed by the pistons, is divided into a series of functional sections represented by the block diagram in FIGURE 2. In successive order from the intake point, the tube is provided with a preheat section 30, an 'evacuation section 32 and a pressure impregnation section 34.

The preheat section 30 is in communication with pipe 38 which leads therefrom and is joined in free communication to a pipe 40 which extends from the vacuum section 32 vertically up to the air ejector 42. The air ejector 42 has communication with a source of steam 44 and an outlet for discharging air through a pipe 46. By suitable valving means, steam is fed through the pipe 44 and allowed to flow through the air ejector down the pipe 40 to its junction with pipe 38 where it is thence by-passed to the pipe 38 into the preheat section. Then, in timing with the travel of the chambers through the tube, the air ejector is actuated and, when the chamber 20 which was subjected to the steam, arrives at the evacuation section, the air is withdrawn therefrom through the pipe 40, air ejector 42, and expelled to the atmosphere by the pipe 46.

The pressure impregnation section has a series of pipes 48 opening in communication therewith to simultaneously and continuously subject a plurality of chambers 20 to liquor impregnation. By means of an intermediate pipe 50 the pipes 48 are in series communication with a common pipe 52 leading from the source of an appropriate known chemical used for this process.

In the preferred method of this invention for treatment of Wood chips, the chips are preheated to a temperature not exceeding 200 F., or subjected to a vacuum of 28" of mercury, or both. An appropriate digesting means, such as soda liquor, is then introduced at 50 to 200 p.s.i. and at temperatures ranging from ambient to 390 F. The liquor impregnation step might involve direct contact of the Wood chips with cold liquor at low pressure followed by the introduction of steam to create pressure and temperature conditions previously mentioned. The composition of the liquor would depend upon the species of wood, the quality of product desired and the operating conditions selected.

After the wood chips have been impregnated the Waste liquor and Wood products are drained and the treated wood chips, now consisting primarily of Wood fibers only, are discharged to atmosphere. From the discharge point the treated pulp may then be formed into mats and shipped to a paper producing mill or may be transferred to the next stage of paper production in the case of an integrated mill.

The method of this invention provides an improved means for more rapid impregnation of wood chips with a digesting liquor to remove the cementing bases therefrom and produce a high quality wood fiber for use in making high quality paper. The method of this invention employs a relatively simple apparatus for its employment and greatly reduces the time involved in producing high grade pulp from wood chips.

Iclaim:

1. The method of making pulp consisting of the steps of: preheating Wood chips in steam to approximately 105 C. to 120 C., thence subjecting said wood chips to a vacuum of approximately 28" of mercury and then subjecting said wood chips to a digesting liquor at temperatures elevated above ambient and a pressure "range of to 200 p.s.i. to impregnate said chips thereby, said digesting liquor being chosen from the class consisting of suliite, soda, sulfate, sodium sulte, and sodium bicarbonate, and thence draining the excess liquor therefrom to produce pulp thereby.

2. The method of making pulp consisting of the steps of: passing a seri'es of closed chambers past a feeding station and introducing wood chips successively into said chamber, thence continuously and successively passing said chambers past a preheating station at which the wood chips are subjected to steam and are preheated at approximately C. to 120 C., thence passing said chips past an evacuating station at which the air is removed from each chamber to produce a vacuum of approximately 28 of mercury and thence passing said chips past an impregnation station at which soda liquor is introduced at a pressure range of 50 to 200 p.s.i. and at at temperature from ambient to 390 F. to impregnate said chips thereby, and thence passing said chamber past a draining station at which the excess soda liquor and waste is drained therefrom to produce pulp thereby.

References Cited by the Examiner UNITED STATES PATENTS 480,334 8/1892 Maste. 1,138,907 5/1915 Thickens. 1,413,716 4/1922 Fish 162-53 2,425,335 8/1947 Messing 162-17 2,675,311 4/ 1954 Natwick 162-19 3,076,501 2/1963 Schinn 162-237 FOREIGN PATENTS 333,426 8/ 1930 Great Britain.

MORRIS O. WOLK, H. R. CAINE, Assistant Examiners.

DONALL H. SYLVESTER, Primary Examiner. 

1. THE METHOD OF MAKING PULP CONSISTING OF THE STEPS OF: PREHEATING WOOD CHIPS IN STEAM TO APPROXIMATELY 105*C. TO 120*C., THENCE SUBJECTING SAID WOOD CHIPS TO A VACUUM OF APPROXIMATELY 28" OF MERCURY AND THEN SUBJECTING SAID WOOD CHIPS TO A DIGESTING LIQUOR AT TEMPERATURES ELEVATED ABOVE AMBIENT AND A PRESSURE RANGE OF 50 TO 200 P.S.I. TO IMPREGNATE SAID CHIPS THEREBY, SAID DIGESTING LIQUOR BEING CHOSEN FROM THE CLASS CONSISTING OF SULFITE, SODA, SULFATE, SODIUM SULFITE, AND SODIUM BICARBONATE, AND THENCE DRAINING THE EXCESS LIQUID THEREFROM TO PRODUCE PULP THEREBY. 